1. Field of the Invention
The present invention relates to oil skimmers, and more particularly, to an apparatus for removing oil from the surface of a liquid.
2. Description of Related Art
There are a variety of types of oil skimmers currently in use. Disk skimmers, belt skimmers, mop skimmers, and tube skimmers are some of the most popular types of skimmers.
Disk skimmers combine a plastic or metal disk with a wiper blade that scrapes the oil from the disk. The disk is rotated and made to come into contact with a small portion of the liquid surface in a tank. Oil must move into contact with the disk before being removed. Also, a disk skimmer can discharge oil at a height no more than the diameter of the disk above the liquid surface in the tank. If the liquid level in the tank is more than a few inches below the edge of the tank it is not possible to use a disk skimmer. Similarly, since disk skimmers will not work if the liquid level falls below the bottom of the disk, they are ill-suited for use on tanks with fluctuating levels. In addition, since the discharge of the oil is so close to the surface of the liquid, additional mechanisms are required to remove the oil from submerged tanks or sumps that have liquid levels close to floor level.
A belt skimmer is another type of oil skimmer. The belt skimmer includes a plastic or metal belt, a scraper for removal of oil, and a pulley, mounted underneath the surface of the liquid, around which the belt runs. In similar fashion to a disk skimmer, a belt skimmer depends on the migration of oil to a surface area which comes in contact with only a small portion of the liquid surface, namely, the belt. The pulley element typically suffers from several drawbacks. Since the pulley has to be inserted in the liquid, fluctuations of the liquid level can prevent the skimmer from working. Also, contamination of the liquid can occur if the pulley is not compatible with the liquid from which the oil is to be skimmed. In addition, more space is required than is available on some machines to allow the pulley to come into contact with the liquid.
Another type of oil skimmer is the mop skimmer, which consists of a loop of stringy oleophilic material to collect the oil, rollers to squeeze the oil from the mop, and a motor to pull the loop of mop material through the rollers and back into the tank. A disadvantage to the mop type skimmers is the possibility of strands of the mop coming loose and damaging the machine if they are picked up by the pump. Another disadvantage to the mop skimmer is that a large quantity of water is picked up with the oil so disposal costs are higher. A still further disadvantage of the mop skimmer is that the rollers are not very efficient in removing the oil from the mop material. Therefore, the mop material going back to the tank cannot pick up as much oil, thereby taking more time to remove the same amount of oil.
Another type of skimmer uses an oleophilic tube to collect and remove the oil. This type of skimmer includes a tube, scrapers, and means to pull the tube out of the tank and through the scrapers. The skimmer can be used when the liquid level is below the floor or if the liquid level fluctuates. Since the tube is cylindrical the minimum radius that the tube can be bent without affecting the operation of the skimmer is a function of the diameter, wall thickness and material of the tubing. The wall thickness of the tube has to be set depending on the rigidity of the material used and how the material is affected by wear. Since the material is selected for its ability to attract oil, the only variable that can be adjusted to change the minimum radius at which the tube can be bent is the radius. Decreasing the radius decreases the surface area of the tube and the amount of oil that can be picked up is reduced proportionally. In a belt skimmer the minimum radius of bend is determined by the thickness of the belt. The belt thickness is independent of the width of the belt so the surface area and therefore the amount of oil removed can remain the same even though the skimmer can work in smaller areas. Since the belt can be bent into a smaller radius the skimmer can be used on smaller tanks and narrower openings.
Applicant is aware of the following U.S. Patents concerning oil removal apparati.
__________________________________________________________________________ U.S. PAT. NO. INVENTOR ISSUE DATE TITLE __________________________________________________________________________ 1,703,963 Scruby Mar 5, 1929 MEANS FOR RAISING OIL FROM WELLS 3,668,118 Rhodes Jun 6, 1972 OIL MOP AND METHOD OF USING SAME 3,774,685 Rhodes Nov 27, 1973 OIL MOP METHOD AND APPARATUS FOR PRODUCING AN OIL WELL 4,388,188 Morris Jun 14, 1983 OIL SPILL RECOVERY MEANS 3,983,034 Wilson Sept 28, 1976 APPARATUS AND METHOD OF REMOVING DEBRIS FLOATING ON A BODY OF WATER 4,673,497 Lundin Jun 16, 1987 OIL-SPILL-COMBATING WATERCRAFT 4,690,093 Lundin Sept 1, 1987 OIL-SPILL-COMBATING WATERCRAFT 4,818,399 Midkiff Apr 4, 1989 OIL SPILLAGE RECOVERY ARRANGEMENT __________________________________________________________________________
Scruby teaches an endless belt that moves down into an oil well and lifts the oil that adheres to it as a heavy film. At ground level, the belt passes around a pulley with a second pulley bearing against the belt; which tends to force the oil off the belt into adjacent troughs.
Rhodes '118 and '685 both teach an oil mop for removing oil from the surface of a body of water. The oil is removed from an endless belt mop by squeezing it through ringers.
Morris teaches boons for confining an oil slick on the high seas, but does not show any scraping device similar to the present invention.
Wilson teaches means for skimming oil from a body of water and discloses that oil removed from a belt into a collection pan by a roller or wiper.
Lundin '497 teaches a separating means, but it does not appear to be a belt scraper.
Lundin '093 shows an endless belt with scraping means, but it scrapes only one side of the belt.
Midkiff teaches another oil recovery arrangement which utilizes siphoning for separating and does not use any belt or scrapers.
None of the related art appear to disclose the structure, operation, and result of the present invented method and apparatus for removing oil from a liquid surface.